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United grates Patent @?tice
1
2
to the cyanide group. Among the compounds which are
3,056,751
known to polymerize to form the triazine ring are: cyan
CARBON-NITROGEN POLYMERS AND NIETHUD
. _
3,056,751
Patented Oct. 2, 1962
ogen chloride, benzonitrile, trichloroacetonitrile, cyanic
OF PREPARWG SAME
acid, and cyanafnide. On the other hand, polymeriza
William L. Fierce, Crystal Lake, and Walter J. Sandner,
Carpentersville, 113., assignors to The Pure Oil Com
tion to form the triazine ring has never been reported
pany, Chicago, iii, a corporation of Ohio
for cyanogen, hydrogen cyanide, acrylonitrile, acetoni
trile, or propionitrile. The polymerization to tricyano
No Drawing. Filed May 28, 1959, Ser. No. 816,392
9 Claims. (Cl. 260-1)
triazine has been accomplished only by means of a multi
This invention relates to new and useful improvements
in methods for preparing carbon-nitrogen polymers, and
more particularly to an improved method for polymeriz
lug cyanogen or hydrogen cyanide by contact at ambient
temperatures with an aqueous solution of a weak acid and
a cyanide salt.
15
Cyanogen, (CN)2 is a well-known compound which
is useful as an organic intermediate, and because of its
high toxicity has found some use as a fumigant. In re
cent years, cyanogen has been evaluated as a rocket pro
step process involving: (1) dehydration of ethyl oxamate
to ethyl cyanoformate, (2) polymerization of ethyl cyano~
formate to triethylcarboxytriazine, (3) aminolysis of the
triazine product to the corresponding amide, and (4) de
hydration of the amide to tricyanotriazine. See E. Ott,
Ben, 52, 660 (1919).
Cyanogen, however, is known to polymerize to form
a material known as paracyanogen, a black, highly inert
solid of high molecular weight. The properties of this
solid are relatively well de?ned and numerous methods
for its prepartion have been reported. Paracyanogen is
pellant and found to have only marginal value because
believed to be a long ribbon-shaped molecule, of inde?nite
of its toxicity and its extremely high combustion tempera
length and molecular weight, of the general formula:
ture (cyanogen and oxygen burn with the hottest ?ame
produced by a chemical reaction). The construction
materials presently used in rocket engines cannot handle
the high temperature produced by a cyanogen ?ame and 25
the toxicity of the compound is a substantial obstacle to
its utilization. One possible solution to the problems of
using cyanogen as a rocket fuel lies in converting it to a
solid polymer. At the present time, solid propellants are
Paracyanogen is a dark, brownish-black solid material
which is insoluble in Water, organic solvents, and liquid
widely used in both military and non-military rockets. 30 cyanogen. It is insoluble in nitric acid but is partially
soluble in strong caustic solution. It is also reported that
It has been thought that solid polymers of cyanogen might
paracyanogen dissolves in cold, concentrated sulfuric acid
and can be recovered unchanged as a precipitate by dilu
tion with water. It can be completely converted into
Tricyanotriazine, which is also called cyanuric cyanide,
can be considered to have the following structure:
35 cyanogen gas by heating to about 860° C. in a current of
be less toxic and have a sufficiently reduced flame tem
perature as to be useful as a rocket fuel.
an inert gas such as nitrogen or helium.
GN
NC
0:2
The molecular
weight of paracyanogen is unknown and, in fact, in~
de?nite, and so it is commonly designated as (CN)X.
Many methods for the preparation of paracyanogen
40 have been reported: V. Migrdichian, “The Chemistry of
Organic Cyanogen Compounds,” 1947, p. 362; H. E.
N
(ii-ON
Williams, “Cyanogen Compounds,” 1948, p. 4; Beilsteins
Because of its composition, containing nothing other than
Handbuch der Organischen Chemie, 2 511 (1942), sec
3 mols of cyanogen, tricyanotriazine can be considered to
ond supplement; and L. L. Bircumshaw, F. M. Taylor and
be a trimer of cyanogen. However, in spite of this fact 45 D. H. Whi?en, J. Chem. Soc., 1954 931. Some of these
of constitution, tricyanotriazine has never been prepared
methods for the preparation of paracyanogen are as fol
lows:
by the condensation of polymerization of cyanogen. The
nitrile (or cyanide) group in organic compounds is un
(l) Paracyanogen forms when cyanogen is heated at
saturated in character and is highly reactive. Many of
atmospheric pressure at 310° C. or at lower temperatures
the reactions of the nitriles depend upon the ability of
under higher pressures. When the pressure is 300 atmos
the carbon-nitrogen bond to add other groups. Examples
pheres the temperature required is 220° C.
of reactions which involve such addition are the hydrolysis
(2) Paracyanogen can be produced by the electrolysis
of potassium cyanide solutions.
of nitriles t0 carboxylic acids, and the formation of imino
ethers by reaction with alcohols. The tendency of many
(3) Photopolymerization of cyanogen has been re
nitriles to polymerize under the influence of certain re 55 ported, as has polymerization initiated by alpha particles.
agents is another example of this reactivity at the carbon
(4) Heating oxamide at 250°—300° C. in a sealed
nitrogen triple bond. Although this tendency is shown
tube yields paracyanogen.
by all types of nitriles, the polymeric products differ in
(5 ) Both cyanogen and paracyanogen are formed when
type depending upon the type of nitrile, and the condi
either silver cyanide or mercuric cyanide is heated in a
tions under which polymerization takes place. in numer 60 sealed tube above about 300° C.
ous cases, nitriles polymerize to form trimeric polymeri
It is therefore one object of this invention to provide
zation products in which three nitrile groups combine to
new ‘and improved carbon-nitrogen polymers which are
form the triazine ring:
derived from cyanogen or hydrogen cyanide.
Another object of this invention is to provide a new
and improved method for polymerizing cyanogen or hy
drogen cyanide to produce solid, stable polymers.
3 R-GN ——>
where R is any radical.
takes place only when no
H
I
A feature of this invention is the provision of a new
carbon-nitrogen polymer prepared by polymerizing cy
anogen or hydrogen cyanide by contact with a catalyst
70 at room temperature.
Polymerization of this type
Another feature of this invention is the provision of
H or CH2 group is attached
an improved method for polymerizing cyanogen or by
3,056,751
3
4
drogen cyanide by contact with an aqueous solution of a
weak acid and a cyanide salt at room temperature.
Other objects and features of this invention will be
hydrogen, 43.0% nitrogen, and 19.2% unidenti?ed resi
due. This paracyanogen was also decomposed by heating
come apparent from time to time throughout the speci?
mal decomposition products analyzed. The non-volatile
cation and claims as hereinafter related.
This invention is based upon our discovery that novel
carbon-nitrogen polymers are obtained, which do not have
residue consisted of only 1% of the weight of the para
the properties of either tricyanotriazine or paracyanogen,
44.3% cyanogen and 8.2% hydrogen cyanide. This para~
to 850°—900° C. for a period of 2-3 hours and the ‘ther
cyanogen. Unidenti?ed volatile matter constituted 46.5%
of the weight of paracyanogen, and there was obtained
cyanogen was burned in oxygen and found to have a heat
with an aqueous solution of a weak acid (such as acetic, 10 of combustion of 6860 b.t.u./1b. From these experi
ments, it is seen that the product which we have obtained
tartaric, boric, carbonic, hydro?uoric, chloracetic, citric,
when hydrogen cyanide or cyanogen is stored in contact
dimethylmalonic, ethylmalonic, formic, glutaric, malonic,
is a polymer having properties which are markedly dif
etc. acids) containing a molar excess of a water-soluble
ferent from the paracyanogen which is obtained in ac
cyanide salt, e.g., NaCN, KCN, NH4CN, Mg(CN)2, etc.
cordance with classical procedures.
In carrying out this invention, the conditions of opera
When hydrogen cyanide or cyanogen is stored in contact 15
tion are not particularly critical. This process is oper
with such an acid-cyanide solution at ambient tempera
ative over a wide range of pressures, from atmospheric
ture for an extended period of time, a solid black polymer
pressure to as much as 1000 atmospheres or higher. The
is obtained which is neither tricyanotriazine or paracyano
process is operative over a wide range of temperatures,
gen. The hydrogen cyanide or cyanogen may be polym
erized at atmospheric pressure or at superatmospheric 20 from as low as 0° to as high as 100° C. or higher. The
reaction proceeds satisfactorily, however, at ambient tem
pressures ranging up to as much as 1000 atmospheres.
peratures, preferably room temperature. The only factor
The reaction proceeds satisfactorily at room temperature
which appears to be critical in the process is the propor
but the process is operative at temperatures in the range
tion of soluble cyanide salt, as previously described. The
from 0° to 100° C.
The following non-limiting examples are illustrative of 25 amount of water-soluble cyanide salt present must be in
a molar excess over the cyanogen. However, there is no
the scope of this invention:
known
upper limit to the amount of water-soluble cyanide
Example I
salt which may be used in this process. Also, the reac
A glass vial of 220 ml. volume was charged with 15 g.
tion time is not critical. While the initial reaction was
sodium cyanide, 25 ml. water, 25 ml. glacial acetic acid, 30 allowed to proceed for 5 weeks, such a long reaction time
and 14.0 g. cyanogen. The vial was sealed and allowed
is not necessary because a large amount of black solid
to stand at room temperature, with occasional agitation,
was observed to form during the ?rst day of the reaction.
for 5 weeks. At the end of this time, the vial was opened
Example 11
and the volatile material was allowed to escape into a
In another experiment, several glass vials were charged
hood. A black solid precipitate was recovered, puri?ed 35
with reactants, sealed, and allowed to stand at room tem
by extraction with boiling water, and dried. The product
perature for 60 days with occasional agitation. One vial
which was obtained amounted to 8.97 g. of a black, odor
was charged with 25 ml. glacial acetic acid, 25 ml. water,
less solid. This solid was insoluble in all common sol
and 7.2 g. hydrogen cyanide. No polymeric product was
vents.
The formation of the black polymer is dependent upon 40 obtained. A second vial was charged with 25 ml. glacial
acetic acid, 25 ml. water, 5 g. sodium cyanide, and 6.3 g.
the amount of water~soluble cyanide salt (e.g., sodium
hydrogen cyanide. At the end of the 60-day period no
cyanide) present in the reaction mixture. No reaction
product had formed. A third vial was charged with 25
occurs in the absence of sodium cyanide. Also, if sodium
ml. glacial acetic acid, 25 ml. water, 15 g. sodium cyanide,
cyanide is present in only catalytic amounts (less than a
1:1 mol ratio of sodium cyanide to cyanogen), the cyano 45 and 7.3 g. hydrogen cyanide. At the end of the reaction
period, there was recovered 11.8 g. of a black solid ma
gen is hydrolyzed rather than polymerized. This process
terial which was recovered by ?ltration, followed by water
is therefore dependent upon the presence of the water
washing and drying. This black solid was odorless and
soluble cyanide salt in a mol ratio of cyanide salt to
cyanogen which is greater than 1:1.
insoluble in all common solvents.
The fourth vial was
The standard analytical laboratory techniques for anal 50 charged with 25 ml. glacial acetic acid, 25 ml. water, 30
g. sodium cyanide, and 7.1 g. hydrogen cyanide. At the
ysis of nitrogen are inaccurate when applied to nitrogen
containing polymers such as paracyanogen, and it was
therefore impossible to obtain a precise and exact analysis
of the polymeric products. However, the black, solid
end of the reaction period, there was recovered 9.4 g. of
a black solid polymer which was recovered by ?ltration,
followed by water washing and drying. A ?fth vial was
polymer obtained in this experiment was analyzed for 55 charged with 25 ml. glacial acetic acid, 25 ml. water, and
15 g. sodium cyanide to determine whether or not sodium
carbon, nitrogen, and hydrogen, and was subjected to
cyanide alone would polymerize under the reaction con
thermal decomposition by heating at 850°~900° C. for
ditions. At the end of the 60-day period, no polymer
a period of 2—3 hours. With common methods of anal
was obtained from this vial.
ysis, composition of the polymer was: 35.9% carbon,
3.9% hydrogen, 37.3% nitrogen, and 22.9% unidenti?ed 60 The solid polymers obtained from the third and fourth
reaction vials were analyzed for carbon, hydrogen, and
residue. When the polymer was decomposed by heating
nitrogen content, and were also subjected to thermal
to 850°~900° C. for 2-3 hours, there was left 10.7% of
decomposition at 850°-900° C. The polymer obtained
the polymer as a non-volatile residue. The volatile prod
from the third and fourth vials contained 34.5% carbon,
ucts of the decomposition contained 14.9% cyanogen,
22.2% hydrogen cyanide, and 52.2% of unidenti?ed ma 65 4.2% hydrogen, 35.7% nitrogen, and an unidenti?ed
residue of 25.6%. Thus the polymer is seen to have a
terial, referred to the whole polymer. This polymer was
carbon, hydrogen, nitrogen, and residue content which
also burned in oxygen and found to have a heat of com
corresponds closely to the cyanogen polymer obtained
bustion of 7030 b.t.u./lb. The solid polymers which are
in Example I, but differs markedly from the composition
produced in this experiment are useful as a solid high
energy rocket fuel and are also useful as a non-toxic 70 of the paracyanogen obtained by pyrolysis of mercuric
cyanide. As mentioned, the polymers obtained in Ex
solid source for evolving cyanogen and/ or hydrogen cy
periments 3 and 4 were subjected to thermal decompo
anide.
sition at 850°—900° C. The products of decomposition
For comparison, paracyanogen was prepared by heating
consisted of 10.7% cyanogen, 24.4% hydrogen cyanide,
mercuric cyanide to 590° F. The black solid paracyano
gen which was obtained analyzed: 36.5% carbon, 1.2% 75 12.3% non-volatile residue, and 52.6% unidenti?ed vol
1
5
3,056,751
atile material, referred to the Weight of Whole polymer.
Again, the decomposition products of this polymer cor
respond closely to the decomposition products obtained
from the cyanogen polymer described in Example I,
rather than the decomposition products of paracyanogen
obtained from mercuric cyanide.
The polymer obtained in Experiments 3 and 4 had
a heat of combustion of 8260 B.t.u./1b. and may be
used as a solid rocket fuel. This polymer is also useful
as a stable, solid, non-toxic source for cyanogen or hy
drogen cyanide since both of these compounds are lib
erated from the polymer upon heating.
While We have described our invention fully and com
pletely, as required by the patent laws, with special
emphasis upon several preferred embodiments of the
invention, 'we wish it to be understood that within the
scope of the appended claims this invention may be prac
ticed otherwise than as speci?cally described herein.
What is claimed is:
1. A method of preparing carbon-nitrogen polymers .
which comprises contacting a cyanide compound selected
from the group consisting of cyanogen and hydrogen
cyanide with an aqueous solution of a Weak acid selected
from the group consisting of acetic acid, tartaric acid,
chloracetic acid, citric acid, dimethylmalonic acid, ethyl~
malonic acid, malonic acid, glutaric acid, formic acid,
boric acid, carbonic acid and hydro?uoric acid and a
Water-soluble cyanide salt, at a mol ratio of cyanide
salt to cyanide compound greater than 1:1, at ambient
temperature for a time sufficient to effect the formation
of a black solid polymer, ‘and recovering the polymer
from said solution.
2. A method in accordance with claim 1 in which
6
the reaction temperature is in the range from about 0°
to 100° C.
3. A method in accordance with claim 2 in which the
reaction pressure is in the range from atmospheric pres
sure to 1000 atmospheres.
4. A method in accordance with claim 1 in which
the weak acid is acetic acid.
5. A method in accordance with claim 1 in which the
cyanide salt is sodium cyanide.
6. A method of preparing carbon-nitrogen polymers
which comprises contacting hydrogen cyanide with an
aqueous solution of acetic acid and sodium cyanide, at
2. mol ratio of sodium cyanide to hydrogen cyanide
greater than 1:1, at a temperature of 0°~100° C., for
a time su?icient to effect the formation of a black solid
polymer.
7. A method of preparing carbon-nitrogen polymers
which comprises contacting cyanogen with an aqueous
solution of acetic acid and sodium cyanide, at a mol
ratio of sodium cyanide to cyanogen greater than 1:1,
at a temperature of ‘0°—100° C., for a time su?icient to
elfect the formation of a black solid polymer.
8. A carbon-nitrogen polymer produced in accordance
with claim 6, containing carbon and nitrogen in substan
tially a 1:1 atomic ratio and yielding about 15% cyanogen
and 22% hydrogen cyanide upon heating to 850° C.
9. A polymer produced in accordance with claim 7
containing carbon and nitrogen in substantially a 1:1
atomic ratio and yielding approximately 11% cyanogen
and 24% hydrogen cyanide upon heating to 850° C.
No references cited.